The role of taurine in the mammalian central nervous system is being examined by manipulation of the dietary intake of taurine. Three species of primate will be examined: rhesus, cynamolgus and cebus. Animals will be raised from birth using a synthetic formula, as used for human infants, alone or supplemented with the amount of taurine present in primate milk. The rhesus monkeys will be examined for retinal function and simple learning ability. All primates will be examined histologically at sacrifice, and tissue content of taurine, and activity of enzymes involved in taurine biosynthesis measured.